Water filtration and recovery technology is increasingly necessary as water resources are depleted and access to fresh water reservoirs is limited. Additionally, contamination of water sources is occurring from a variety of activities and industries, which include, for example, agricultural, automotive services, and energy exploration. These contaminates include, but are not limited to heavy metals, pesticides, herbicides, antibacterial agents, elevated bacterial levels, detergents, phosphates, petroleum, and petroleum additives. In addition, there is a need for a water filtration system that has a low environmental impact to remove naturally occurring levels of sodium, such as a filtration system to desalinate sea water. A problem exists, then, how to best enable a water filtration system that eliminates unacceptable levels of chemicals, including petroleum contaminates, bacteria, and salts in a water source or supply.
Most of the water that is utilized in certain industrial applications, such as in car washes, must be collected and treated in order to remove contaminants, including petroleum products, pesticides, herbicides, phosphates and detergents.
Additionally, the water that is utilized in other industrial applications, such as energy exploration, including hydraulic fracturing (“fracking”) operations, require the use of large amounts of fracturing fluids. As a result, fracking produces large amounts of waste water that may contain high levels of total dissolved solids, fracturing fluid additives, suspended solids, hardness compounds, metals, oil, gas, bacteria and bacteria disinfection agents, both as a result of the process itself as well as the fracturing fluid used during the processing.
Therefore, there is a need for an alternative to storing wastewater in surface ponds at the fracturing site, or transporting wastewater for disposal or underground injection of wastewater, or transporting wastewater for treatment that will allow drill operators to re-use the wastewater to replace and/or supplement fresh water in formulating fracturing fluid for a future well or re-fracturing the same well.
It would be desirable to provide a water filtration and water recovery system that can collect and recycle the water from various wastewater sources, including petroleum-containing water as well as other contaminants from water utilized in various industrial applications, including but not limited to car washes so that the water can be collected and reused. Such a filtering and recovering system would decrease the overall operation costs of high water usage industries by providing a recyclable water source that may be used for a variety of alternative uses. Filtering and recycling the water from industrial operations would also reduce overall costs by eliminating the cost to service industries and energy exploration companies which must comply with various regulations to prevent the release of contaminated water. An additional benefit of filtering and recycling the water is the decrease in cost of using or purchasing water from the local municipalities supply or from alternative sources. Another key benefit of filtering and recovering the water recovered from industrial applications is that the filtered and recovered water will not contain contaminates typically found in a fresh water supply (such as bacteria or naturally occurring levels of heavy metals).
It would also be desirable to have such recycling occur in a continuous processing (or continuous batch processing) and to be able to produce recycled products in the same operation at a car wash site or fracturing site, without the environmental risk of releasing contaminated water to the local water shed or transporting contaminated water to a treatment facility.
Further, it is desirable to be able to produce a water filtration system that has a low environmental impact and its components could be developed without the use of hazardous reducing agents or stabilizing agents, as used in the production of other filtration systems.
Silver nanoparticles and their nanoscale nanocomposites, have become a subject of intense research interest in various fields of science. This growing interest stems from their unique and exclusive nanoscale physical, optical, and electronic properties tailoring them to widespread range of applications in different scientific and industrial backgrounds.
However the high surface energy and reactivity associated with extremely small diameter nanoparticles often leads to undesirable static electrical combinations or aggregation which adversely affects their most sought-after nanosize associated properties. Since the usefulness of silver particles is nanoscale dependent, the challenge is ensure that the particles do not coalesce and form bulk particles. Thus organic and polymeric surfactants are used to stabilize Ag nanoparticles with small diameters which prevent flocculation and sedimentation during and after synthesis. However the high reactivity of these polymeric surfactants and chemical reducing agents poses biological and other environmental hazards which could potentially limit their use. Moreover the formation of some silver-polymer complexes could block the nanosites of the silver metallic particles reducing the effective utilization of the nanoparticle surfaces.
Due to aforementioned concerns, green techniques are being developed for the production of silver nanoparticles that exclude the use of harsh chemical reducing agents. For instance biodegradable, nontoxic β-D-glucose and starch have been used for the synthesis of silver nanoparticles. These green, inexpensive reducing and capping agents albeit are effective in producing narrow distributed particles, the processing conditions such as high temperatures, pressures and lengthy reaction times require in their hydrothermal associated synthetic techniques lead to formation of bulk particles. Another green technique is the use of organic extracts as reducing and stabilizing agents but the geographical and seasonal variation of the intrinsic active agents in these organic extracts impacts negatively on the consistency of the particle morphology as well as their size.
A promising technique of producing discrete silver nanoparticles is to immobilize the nanoparticles on porous solid supports; this unlike polymeric matrix does not only maximize the exposure of the surface area of the active sites but also increases their aqueous chemical stability. Activated carbon loaded silver nanocomposite have demonstrated improved antimicrobial properties relative to silver nanoparticles. Literature exists on the immobilization of silver nanoparticles on activated carbon supports. In both studies, the silver nanoparticles are immobilized on few oxygenated groups located on the micrometer pores of the activated carbon particles. Thus the amount of silver nanoparticles that can be loaded is depended on the efficiency of functionalization of the activated carbon. Moreover chemical functionalization is laborious and requires harsh environmentally chemical reagents and conditions to be achieved.
Liquid assisted grinding provides an environmentally sustainable route of producing nanomaterials. The sparing or no use of solvents (toxic solvents), accompanying low energy usage and less waste production increase the eco attractiveness of this technique. A one step successful milling synthesis of the Silver (Ag) and Iron (Fe) nano metals has been demonstrated. However solvent free mechano-chemical synthesis introduces particle agglomeration due to the rapid and progressive welding accompanying milling of particles. Conversely wet milling has been shown to restructure particle aggregates leading to reduction of particle size. There thus remains a need for an environmental friendly method of producing silver nanoparticles that would be useful in water filtration systems to kill or inactivate microbes present in water.